广度优先搜索算法陷入无限循环

Question

I am trying to implement a Breadth First Search algorithm for 8puzzle. I am somehow not able to get in the `is(RequiredState(see))` condition where my search terminates. My program gets stuck in an infinite loop. I have put the repeating states in a state to prevent getting stuck in a loop, but somehow my program still gets stuck in a loop.

board.java

        public class board {
            public
                int[] square = new int[9];
            board()
            {
                for(int i=0;i<9;i++)
                {
                    square[i]=8-i;
                    square[8] = 0;


                }
            }
            int findBlankPos()
            {
                for(int i=0;i<square.length;i++)
                {
                    if(square[i]==0)
                    {
                        return i;
                    }
                }
                return 9;
            }
            static int size()
            {
                return 9;
            }
            void moveBlankUp(int blankpos)
            {
                square[blankpos] = square[blankpos-3];
                square[blankpos-3] = 0;
            }
            void moveBlankDown(int blankpos)
            {
                square[blankpos] = square[blankpos+3];
                square[blankpos+3] = 0;
            }
            void moveBlankRight(int blankpos)
            {
                square[blankpos] = square[blankpos+1];
                square[blankpos+1] = 0;
            }
            void moveBlankLeft(int blankpos)
            {
                square[blankpos] = square[blankpos-1];
                square[blankpos-1] = 0;
            }
            boolean canMoveUp(int blankpos)
            {
                if((blankpos==0)||(blankpos==1)||(blankpos==2))
                    return false;
                else
                    return true;
            }
            boolean canMoveDown(int blankpos)
            {
                if((blankpos==6)||(blankpos==7)||(blankpos==8))
                    return false;
                else
                    return true;
            }
            boolean canMoveRight(int blankpos)
            {
                if((blankpos==2)||(blankpos==5)||(blankpos==8))
                    return false;
                else
                    return true;
            }
            boolean canMoveLeft(int blankpos)
            {
                if((blankpos==0)||(blankpos==3)||(blankpos==6))
                    return false;
                else
                    return true;
            }
            void display()
            {
                for(int i=0;i<square.length;i++)
                {
                    if((i)%3==0)
                    {
                        System.out.println();
                    }
                    System.out.print(square[i] + " ");
                }
            }
            Integer getAt(int pos)
            {
                return square[pos];
            }
            void setAt(int pos,int value)
            {
                square[pos] = value;
            }
        }

puzzle.java

    import java.awt.List;
    import java.util.HashSet;
    import java.util.LinkedList;
    import java.util.Queue;
    import java.util.Set;


    public class puzzle {
        public static void main(String[] args)
        {
            board b = new board();
            Set<board> set = new HashSet<board>();
            b.display();
            Queue<board> queue = new LinkedList<board>();
            queue.add(b);
            /*b.setAt(4,0);
            b.setAt(8,4);
            b.display();
            System.out.println();
            AddChildrentoQueue(queue,b);*/

            //System.out.println(queue.);
            int itr=0;
            while(!queue.isEmpty())
            {
                itr++;
                System.out.println(itr);
                board see = queue.peek();
                //System.out.println(count);
                if(!(set.contains(see)))
                {
                    set.add(see);
                    //see.display();
                    //System.out.println();
                    if(isRequiredState(see))
                    {
                        queue.peek().display();
                        System.out.println("End it with a Bang");
                        break;
                    }
                        AddChildrentoQueue(queue,queue.peek());
                        //System.out.println(queue.size());
                        if(itr==1)
                            break;

                }
                queue.remove();
            }
            //System.out.println(isRequiredState(b));

        }

        private static boolean isRequiredState(board peek) {
            // TODO Auto-generated method stub
            String state="";
            for(int i=0;i<peek.size();i++)
            {
                String temp = (String)peek.getAt(i).toString();
                //System.out.println(temp);
                state = state + temp;
            }
            //System.out.println(state);
            if(state.equals("123456780"))
            {
                return true;
            }
            return false;
        }

        private static void AddChildrentoQueue(Queue<board> queue, board b) {
            // TODO Auto-generated method stub
            board d;
            if(b.canMoveUp(b.findBlankPos()))
            {
                d = getClone(b);
                d.moveBlankUp(b.findBlankPos());
                d.display();
                System.out.println();
                queue.add(d);
            }
            if(b.canMoveDown(b.findBlankPos()))
            {
                d = getClone(b);
                d.moveBlankDown(b.findBlankPos());
                d.display();
                System.out.println();
                queue.add(d);
            }
            if(b.canMoveRight(b.findBlankPos()))
            {
                d = getClone(b);
                d.moveBlankRight(b.findBlankPos());
                d.display();
                System.out.println();
                queue.add(d);
            }
            if(b.canMoveLeft(b.findBlankPos()))
            {
                d = getClone(b);
                d.moveBlankLeft(b.findBlankPos());
                d.display();
                System.out.println();
                queue.add(d);
            }


        }
        static board getClone(board b)
        {
            board c = new board();
            for(int i=0;i<c.size();i++)
            {
                c.setAt(i,b.getAt(i));
            }
            return c;
        }


    }

所以这就是我最终解决了我的问题。当我研究这个问题时，我发现当我比较检查的元素是否在集合中时，它实际上比较了地址值而不是对象需要，这就是为什么我无法摆脱无限循环，因为每次生成一个新地址。为了不使用集合比较对象，我创建了一组字符串，比较存储为字符串的对象的配置然后把它放进去。感谢很多让我找到问题的人。真的！

import java.awt.List;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Set;


public class puzzle {
    public static void main(String[] args)
    {
        board b = new board();
        Set<String> set = new HashSet<String>();
        b.display();
        Queue<board> queue = new LinkedList<board>();
        queue.add(b);
        /*b.setAt(4,0);
        b.setAt(8,4);
        b.display();
        System.out.println();
        AddChildrentoQueue(queue,b);*/

        //System.out.println(queue.);
        //int itr=0;
        while(!queue.isEmpty())
        {
            //itr++;
            board see = queue.peek();
            String check = getSequence(queue.peek());
            //System.out.println(itr);
            //System.out.println(check);
            if(!(set.contains(check)))
            {
                set.add(check);
                //see.display();
                //System.out.println();
                if(isRequiredState(see))
                {
                    queue.peek().display();
                    System.out.println("End it with a Bang");
                    break;
                }
                    AddChildrentoQueue(queue,queue.peek());
                    //System.out.println(queue.size());
            }
            queue.remove();
        }
        //System.out.println(isRequiredState(b));

    }

    private static boolean isRequiredState(board peek) {
        // TODO Auto-generated method stub
        String state = getSequence(peek);
        //System.out.println(state);
        if(state.equals("123456780"))
        {
            return true;
        }
        return false;
    }


    private static String getSequence(board peek) {
        // TODO Auto-generated method stub
        String state="";
        for(int i=0;i<peek.size();i++)
        {
            String temp = (String)peek.getAt(i).toString();
            //System.out.println(temp);
            state = state + temp;
        }
        return state;
    }

    private static void AddChildrentoQueue(Queue<board> queue, board b) {
        // TODO Auto-generated method stub
        board d;
        if(b.canMoveUp(b.findBlankPos()))
        {
            d = getClone(b);
            d.moveBlankUp(b.findBlankPos());
            d.display();
            System.out.println();
            queue.add(d);
        }
        if(b.canMoveDown(b.findBlankPos()))
        {
            d = getClone(b);
            d.moveBlankDown(b.findBlankPos());
            d.display();
            System.out.println();
            queue.add(d);
        }
        if(b.canMoveRight(b.findBlankPos()))
        {
            d = getClone(b);
            d.moveBlankRight(b.findBlankPos());
            d.display();
            System.out.println();
            queue.add(d);
        }
        if(b.canMoveLeft(b.findBlankPos()))
        {
            d = getClone(b);
            d.moveBlankLeft(b.findBlankPos());
            d.display();
            System.out.println();
            queue.add(d);
        }


    }
    static board getClone(board b)
    {
        board c = new board();
        for(int i=0;i<c.size();i++)
        {
            c.setAt(i,b.getAt(i));
        }
        return c;
    }


}

Answer 1

在评论中指出了使用散列数据结构而没有实现与hashCode()一致的equals()的问题，因此这里建议您可以将hashCode()用作@Override public int hashCode() { int hashCode = 0; for(int i = 0; i < square.size; i++) { hashcode += (square[i] << (3 + i % 2)*i); } } ：将电路板的单元格视为从左上角到右下角0 <= i <= 8的数字。

int

你最终会得到一个有点粗暴的equals()，但仍然理所当然地来自与你的关注相关的董事会状态，并且肯定与equals()一致，检查是否所有被比较的两块板的单元保持相同的值。如果您确实实施了hashCode()和A.equals(B) -> A.hashCode() == B.hashCode()，请务必执行此操作，这大致意味着

->

其中{{1}}是逻辑含义。